This application is based on an application No. H10-096987 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus comprising an image forming unit and a main controlling unit which can be loaded to be removable to this image forming unit in order to control the image forming unit.
2. Description of the Related Arts
An image forming apparatus is structured by an image forming unit and a main controlling unit for controlling the image forming unit. The image forming unit, which is called in this field xe2x80x9cprint enginexe2x80x9d, comprises a sheet feeding device, a photosensitive drum, a laser scanning device, a developing device, a transferring device, a fixing device and a sub-controller, etc. and forms an image on the sheet supplied thereto. The main controlling unit controls indirectly or directly each part of the image forming unit via the sub-controller explained above. The main controlling unit is called in this field xe2x80x9cprint controllerxe2x80x9d.
When a new type image forming apparatus is developed, the image forming unit and main controlling unit are developed, in many cases, at different developing sections or places. It is natural that in respective specifications of above two units, various contents, such as resolution, image clock frequency, system speed, time from horizontal synchronous signal to beam emission, time from vertical synchronous signal to beam emission and number of rotations of an optical beam deflecting means are determined in detail. The work for determining such specifications and developing works are repeated in many times for every type of apparatus and the resultant cost and time used for development becomes very enormous.
Moreover, if an image forming unit or main controlling unit fails or becomes inoperative because of its life span, many units of a new apparatus obtained at that time have different specifications and therefore the newly obtained unit cannot be connected to the other unit. Even if it may be connected, size of image is different from the preceding image or an image is printed in difference positions in almost every case. Accordingly, it has substantially been impossible to replace the defective unit or the unit manufactured for a new type of apparatus.
Therefore, customers have to purchase a new image forming apparatus and scrap the old image forming apparatus, even if one or another unit can operate normally. As described above, here rises a problem that customers are not only shared excessive cost but also given the increased load to maintain the environmental condition due to scrapping of the old image forming apparatus.
In the image forming apparatus, units or devices thereof are operated with each other by keeping the adequate timing. Japanese Published Unexamined Patent Applications, HEI 5-197263, HEI 5-176130, HEI 5-130335, HEI 6-143698, HEI 5-208522, HEI 4-013364 and HEI 4-296779 disclose the techniques about the operation timing of the unit or device.
For example, the Japanese Published Unexamined Patent Application No. HEI 5-197263 discloses an example that relationship among image clock frequency, number of rotations of polygon mirror and amount of laser beam are changed without change of system speed in the case of changing resolution, an example that relationship among image clock frequency, system speed and amount of laser beam is changed without change in number of rotations of polygon mirror and an example that relationship among number of rotations of polygon mirror, system speed and amount of laser beam is changed without change of image clock frequency. Here, combination of system speed, image clock frequency, number of rotations of polygon mirror and horizontal/vertical direction printing start timing is fixed and resolution is changed by changing such fixed value.
Moreover, the Japanese Published Unexamined Patent Application No. HEI 5-176130 discloses an example that the number of rotations of polygon mirror and laser beam emission timing are changed depending on the communication system G3 and G4 of a facsimile apparatus. Here, combination of the system speed, image clock frequency, number of rotations of polygon mirror and horizontal/vertical direction printing start timing in each resolution is fixed.
The inventions disclosed in above Japanese Published Unexamined Patent Applications does not deal with the subject of the present invention explained above and the image clock frequency, resolution, system speed, horizontal direction printing start timing, vertical direction printing start timing and number of rotations of optical beam deflecting device are previously determined for the main controlling unit and image forming unit. Therefore, if the image forming unit, for example, fails, it cannot be replaced with the image forming unit of the other type of apparatus.
The present invention is intended to provide an image forming apparatus which can combine an image forming unit and a main controlling unit of different types of image forming apparatus.
Moreover, the present invention is intended to provide an image forming apparatus which can automatically set various numerical data by transferring, between the image forming unit and main controlling unit, various pieces of information regarding image clock frequency, resolution, system speed, horizontal direction printing start timing, vertical direction printing start timing and number of rotations of optical beam deflector.
In addition, the present invention is also intended to provide an image forming apparatus which allows a user to replace either old image forming unit or old main controlling unit by the new corresponding unit.
The present invention is further intended to provide an image forming apparatus which assures the printing without any change of image size and deviation of the image writing position even when only one unit is replaced with the unit of the other type of apparatus.
The present invention is moreover intended to reduce economical sharing of user who is purchasing a new image forming apparatus and load on environmental condition due to scrapping of old apparatus.
Furthermore, the present invention is also intended to provide an image forming apparatus which does not require, at the time of developing a new type apparatus, any adjustment of specifications of the image forming unit and main controlling unit and thereby can reduce the load of development from the viewpoint of time and cost.
The image forming apparatus of the present invention comprises a main controlling unit for transmitting an image data synchronously with an image clock, an image forming unit for outputting an image as a visible image on the basis of the image data transmitted from the main controlling unit, a detector for detecting that the main controlling unit and image forming unit are connected, a communication device for transferring a control data between the main controlling unit and image forming unit and a sub-controller for obtaining the information regarding the image clock via the communication device responding to detection by the detector and also calculating the operating conditions of the image forming apparatus using the information regarding the obtained image clock.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of preferred embodiments of the invention which follows. In the description, reference is made to accompanying drawings, which from a part thereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.